So, on my current show, I took over the day after opening, and we are in the middle of US training, cross training crew, training crew subs, and trying to locate a new PA to sub on the deck so the ASM could learn the call - since both the original SM and PA were going to unavailable for most of the month of May.
Thursday of last week, I had to stay home from US rehearsal due to a very quick fever, cold and chills, but was able to come in for the show. Friday, on my way into the show, felt like I was internally stabbed. Made it to the theater, talked my ASM through the calling of the hard parts (this is a four person show, no automation, no may to hurt anyone) - and then went to the hospital - for six days - and will most likely be out another two.
Not an ideal situation at all - but important to note
a) have a plan to train someone to call the show, and talk them through.
b) make sure you calling script is clean and someone else can call from it. There are actually two schools of thoughts on calling script . . . one is to make it so clear anyone can call from it and two is to make a calling script you can call from . . . but maybe not anyone else. (This is an old school method of job security . . . )
c) Make sure not only you have someone who can call the show - for example your ASM . . . but someone to sub for you.
Even for a short run, think of this plan . . . something like this can come up instantly . . . not hit by bus, but a very angry gallbladder which needs to get out . . . can side line you for a bit.